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By Mari, founder of K Skin Aura
Ingredient guide6 min readChecked 8 Nov 2026
Before I got into Korean skincare, I’d heard the word “active” everywhere. I had no idea what it actually meant. Here’s the simple version, how strong each one is, and which one to start with for your skin.
The short answer
An active is an ingredient that’s there to change how your skin works: how fast it sheds old cells, how much oil or pigment it makes, how it repairs. Everything else in the bottle is there to deliver it, protect it, and keep your skin comfortable while it works.
“An active is an ingredient strong enough to change your skin. Which is exactly why it can also upset it.”
MariDoers and carers: the easiest way to think about it
Most of any product is a base: water, oils, moisturisers and preservatives. Inside that base, ingredients do one of two jobs.
Doers (actives)
Change something. Retinoids, exfoliating acids, azelaic acid, vitamin C, niacinamide, tranexamic acid, peptides, PDRN.
Carers
Keep skin comfortable. Ceramides, hyaluronic acid, centella, panthenol, squalane. Not actives, but they’re what let your skin cope with one.
A ceramide cream looks after your skin. A retinal serum tries to change it. The second one is the active. A good routine is one doer at a time, held up by carers.
Why everyone uses the word differently
If you’ve been confused, it isn’t you. In the US, “active ingredient” is a legal term for medicines, which is why American sunscreens and spot treatments print “Active ingredients” on the box. UK skincare labels have no such heading. The rules only ask brands to list ingredients from most to least, by weight, with anything under 1% allowed in any order. They don’t have to print percentages.
So in the UK, “active” is a shopping word, and brands use it for whatever they want to sell. That’s why one brand calls hyaluronic acid an active and another doesn’t.
How strong is each active?
Here’s how likely each one is to irritate when you start. It isn’t a ranking of how well they work.
Gentle
Niacinamide, tranexamic acid, peptides, PDRN.
Good first actives. Usually fine morning and night.
Medium
Azelaic acid, pure vitamin C (L-ascorbic acid), and gentle acid toners with a low AHA or BHA.
A tingle at first is common. The prescription-strength azelaic cream lists burning and itching as very common side effects.
Strong
Retinoid serums (retinol, retinal, HPR) and higher-strength AHA serums or peels.
One per routine, usually at night, built up slowly. SPF every morning. Dryness, redness and burning are common side effects in the leaflet for the retinoid Differin.
The same active can sit higher or lower depending on the strength and the formula. A serum with a very low dose of retinal is gentler than one built around it.
The mistake that taught me this
I once used an exfoliator and a retinoid together. It wrecked my barrier. That’s two strong actives in one go, which is exactly what the British Skin Foundation warns about.
Now I’m 40, and I keep it simple: azelaic acid in the morning, a retinoid at night. One active per routine.
I have rosacea. When I started retinol and retinal, the over-the-counter kind, I had some tingling and an adjustment period, but I’m doing okay with them. That’s my experience, not a rule. Rosacea skin often reacts to retinoids, so try one on a small area first, and ask your GP or pharmacist if your rosacea is being treated.
I’ve also had a little reaction to one of the stronger products I’ve tested. Strong stuff can work, but it’s no joke.
Which active for which skin problem?
Most guides give you five options for every problem. Here’s one to start with.
SpotsAzelaic acid
At 20% it is a licensed acne medicine in the UK. Very oily with blackheads? BHA (salicylic acid) is the other common choice.
RednessAzelaic acid
At 15% it is a licensed rosacea treatment. More in our rosacea routine guide.
Dark marksTranexamic acid
The strongest evidence is for melasma, a common type of dark patch. Add a retinoid later if you want to go further.
Fine linesA retinoid
Retinal or retinol, a few nights a week to start. See which retinal strength to start with.
DullnessNiacinamide
In one study, 5% niacinamide brightened skin within four weeks. Azelaic acid helps too.
Tight, dry or stingingNo active yet
Carers first. Fix the barrier, then add a gentle active. See how to repair a damaged skin barrier.
How to spot an active on a label
Look for these names on the ingredient list. The higher up, the more there is, but an active under 1% can sit anywhere near the end.
Retinoids
Retinol, Retinal, Hydroxypinacolone Retinoate
Exfoliating acids
Glycolic Acid, Lactic Acid, Salicylic Acid, Betaine Salicylate
Azelaic acid
Azelaic Acid
Vitamin C
Ascorbic Acid, or a longer name such as 3-O-Ethyl Ascorbic Acid
Niacinamide
Niacinamide
Tranexamic acid
Tranexamic Acid
PDRN
Sodium DNA
A percentage on the front, like “TXA 6%”, is the brand’s own claim. UK rules don’t require one.
My rules for starting actives
- One active per routine. Add a new one only when your skin has settled.
- Start gentle, and start slowly: a few nights a week for anything strong.
- SPF every morning. Actives are no joke, and a lot of people just slap things on their face. The FDA says exfoliating acids make skin more sensitive to UV.
- Give it time. People expect things to work straight away. Your skin works in cycles, and the older you get, the longer each cycle takes. One study measured the outer layer of skin replacing itself in about 20 days in under-35s and about 28 days in over-60s.
- Pregnant or breastfeeding? Ask your doctor or pharmacist before using any retinoid.
One product for each starting point
1
Spots and redness
Spots and rednessPurito
Azelaic Acid 10 + Kojic + Tea Tree Serum
10% azelaic acid with niacinamide and a little kojic acid. Mari’s morning active. Contains tea tree.
£18.99Add to bag
2
Dark marks
Dark marksPurito
TXA 6% + Niacinamide 10% + Retinal Serum
6% tranexamic acid and 10% niacinamide, with a very low dose of retinal. Mari’s evening active.
£19.99Add to bag
3
Dullness
DullnessSKIN1004
Madagascar Centella Tone Brightening Capsule Ampoule
Niacinamide, tranexamic acid and a vitamin C derivative. No retinoid or exfoliating acid listed. A gentle first active.
£20.50Add to bag
4
Fine lines
Fine linesDr.Reju-All
0.1% HPR, a retinoid, with 10% niacinamide and tranexamic acid. Evenings, 2 to 3 nights a week to start.
£27.90Add to bag
5
The carer
The carerPurito
Wonder Releaf Centella Serum Unscented
An unscented centella serum to calm skin after your active, morning and night.
£18.99Add to bag
6
Every morning
Every morningKnours
Koolsol Ultra Light Invisible Mineral Sunscreen SPF50
A light mineral SPF50. Non-negotiable once you use actives.
£26.99Add to bag
Mari’s two actives: Purito azelaic acid (morning) + Purito TXA retinal (evening)
£38.98 · one active per routine
More on each: how to use azelaic acid · what you can mix with it · starting retinal after 40 · the anti-ageing ingredients guide
Not sure which active you need?
Send me what you use now. I’ll reply personally with which active I’d start with, what I’d pause, and the order I’d use it in. You don’t have to buy anything.
Ask meSkin Advice is a cosmetic routine review. It is not a diagnosis.
Frequently asked questions
What counts as an active ingredient in skincare?
An ingredient that is there to change how your skin works: how fast it sheds old cells, how much pigment or oil it makes, or how it repairs. Retinoids, exfoliating acids (AHA and BHA), azelaic acid, vitamin C, niacinamide, tranexamic acid, peptides and PDRN are the common ones. Ingredients that mainly hydrate or soothe, such as ceramides, hyaluronic acid and centella, support your skin rather than change it.
Is hyaluronic acid an active?
Some brands call it one, but it mainly holds water in the skin. In this guide it is a support ingredient: it keeps skin comfortable while your active does its job.
Is niacinamide an active?
Yes, a gentle one. In a 2002 study in the British Journal of Dermatology, a 5% niacinamide moisturiser reduced the look of dark patches and made skin look lighter within four weeks.
How many actives should you use at once?
Start with one per routine. For example, azelaic acid in the morning and a retinoid at night. Add a new active only once your skin has settled on the last one.
Can sensitive skin use actives?
Often, yes, if you start with a gentle one, introduce one product at a time and try it on a small area first. If your skin is being treated for a condition such as rosacea, ask your GP or pharmacist first.
Do I need SPF if I use actives?
Yes, every morning. The US Food and Drug Administration says exfoliating acids (AHAs) make skin more sensitive to UV, and retinoid leaflets advise avoiding strong sun.
How long do actives take to work?
Weeks, not days. Your skin renews in cycles, and the cycle slows with age. One study measured the outer layer replacing itself in about 20 days in under-35s and about 28 days in over-60s.
Can I use actives when pregnant or breastfeeding?
Ask your doctor or pharmacist first, especially for retinoids. The patient leaflet for the prescription retinoid Differin says not to use it if you are pregnant or planning a pregnancy.
About Mari. Mari is the founder of K Skin Aura, a UK Korean skincare retailer. She has been obsessed with skincare since her teens and experimented heavily, which damaged her skin barrier. She rebuilt it by learning to read ingredient lists and studying Korean skincare, which she loves. After a trip to South Korea she started selling Korean skincare in April 2025. She reviews cosmetic routines and product choices through K Skin Aura's free Skin Advice service. She is not a dermatologist or clinician.
Sources checked. US Code of Federal Regulations, 21 CFR 210.3 (definition of active ingredient) · Cosmetics Regulation 1223/2009, Article 19 (labelling), as retained in UK law · British Skin Foundation: which pharmaceutical skincare you shouldn’t mix and why · US Food and Drug Administration: alpha hydroxy acids · Differin Cream patient leaflet · Skinoren 20% Cream patient leaflet · Scottish Medicines Consortium: azelaic acid 15% gel (Finacea) · Tranexamic acid in melasma: meta-analysis, Acta Dermato-Venereologica 2017 · Hakozaki et al., niacinamide and pigmentation, British Journal of Dermatology 2002 · Ageing skin barrier review, Journal of Cosmetic Science (skin turnover data) · Product directions and ingredient lists, checked 8 November 2026
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